Honda, the power unit supplier to blame for the McLaren Formula One team’s miserable lack of reliability lately, admitted that their MGU-H design—a key component of their engine’s hybrid system—can only last two races, reports Motorsport.com. MGU-H stands for “motor generator unit-heat,” as it recaptures heat energy from the exhaust to use to power the car.

Honda F1 head Yusuke Hasegawa isn’t quite sure what causes the problem, but told Motorsport.com that it relates to the rotation of a bearing, and said that more work is needed to make it last longer than two races:

Every two races we need to change – that is not acceptable. We think we need to have more modifications for robustness, with the rotating parts especially.

﻿Currently we are controlling some temperatures or behavior. We can manage the reliability. This time it did OK [mileage wise], but still we are having some issues for reliability.

This admission comes on the heels of Jenson Button’s 15-place grid penalty at this weekend’s Monaco Grand Prix for McLaren having to change the MGU-H and turbo on his car after Thursday’s practice sessions. Button, who is filling in for Fernando Alonso this weekend, is driving a car that’s on its fifth MGU-H and turbo of the season.

You’re only allowed four of each of the major power unit components per season, and McLaren is already incurring grid penalties for power unit component swaps. It’s only May, and the season ends in November. That’s horrific.

McLaren already modified their MGU-H for reliability after a string of failures in Bahrain last month, but it has not been enough.

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Worse yet, the tight, narrow Monaco Grand Prix circuit where passing is exponentially more difficult than most circuits of the season is one of McLaren’s best chances at scoring points all season. Button qualified ninth this morning, but will be moved to the back of the grid for the changes made to his Honda power unit after Thursday’s practice.

Hasegawa told Motorsport.com that irregularities with the rotation of the MGU-H forced them to swap the parts on Button’s engine:

After running FP2 we normally check every rotation part – engine, MGU-H – and we saw the MGU-H rotating a little bit odd for a normal situation.

It’s not completely strange, but the mechanics felt some friction. When we have a complete MGU-H failure, the MGU-H turbine is completely stuck. Seized. This time there is not such a problem, but the mechanics could feel some resistance.

We discussed things with the Japanese side and we decide to change on Friday morning. That is a 100,000 rpm part, and if we feel something strange, it never lasts. It had some chance, but it’s not worth it.

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You would think with so many failures, Honda would have had this figured out by now. Either way, it’s appalling that one of the most crucial parts of Honda’s power units isn’t built to withstand more than two races.